What Can a Drone Actually “See”?
I think the UAV industry in general and the search & rescue community in specific should do a lot more work on designing and performing experiments with UAVs. Vendors and sales outlets keep touting their UAVs as being “good for search & rescue” without providing any data to support this claim, and often without really understanding SAR, SAR missions, and the challenges we face. (More on this in my upcoming presentation for NAASIC in Reno in September.) On the privacy side, people claim “he couldn’t see anything at 200 feet with that drone.” or the opposite position without sharing any data to support these claims.
Since I am an engineer, I like to gather data to support conclusions. And, for similar reasons, I usually form a hypothesis prior to conducting an experiment. Full disclosure – the data did not support my hypothesis. I’ll explain at the end of this post.
For the tl;dr folk – you cannot see much detail in a stock Phantom 2 Vision+ image when taken more than 50 feet above the subject.
This experiment was conducted with a stock DJI Phantom 2 Vision+. The lens specifications, according to DJI, are:
- Sensor Size – 1/2.3″
- Effective Pixels – 14 Megapixels
- Resolution – 4384×3288
- Recording FOV -110° / 85°
I had the camera set to use the “large” photo size and thus the full resolution.
The items in the frame are:
- A black Pelican case
- A human male wearing blue jeans and a reddish t-shirt
- A high visibility orange long sleeve thermal shirt
- A light blue t-shirt
- A white board with black writing on it
The sky was overcast and the winds were between 5 and 15mph out of the south east. I took the Phantom up to 25, 50, 100, 150, 200, 250, and 300 feet, +/- 3 feet as reported by DJI’s Vision app. At each altitude I took a single photograph. After landing, I used Photoshop to zoom in to approximately the same area in each image.
In the raw images viewed natively without any zoom:
- It is hard to find any identifying details of a human in the image above 50 feet.
- At 200 feet it would be hard to identify the human if you did not know what you are looking at.
Using the zoom tool in Photoshop:
- Detail is hard to discern at 100 feet and very difficult past 100 feet
- Given the subject’s pose you can determine that there is a human in the frame up to 300 feet.
- If you thought a drone would be invading your privacy when flown at 200 feet do you still feel this way after looking at these images?
- If you want to use a drone to search for missing people, do these images help you determine your mission parameters and effectiveness?
And my hypothesis? I thought more detail would be available further up. Glad I’m conducting experiments.
Image analysis is not my forte. If you have additional observations, please comment or share them with me directly and I’ll get them included.